1. Field of the Invention
The present invention relates to a system for manufacturing a culture medium for cultivating mushrooms or the like, and more particularly to a system for manufacturing a solid medium by fully automating the steps of mixing, sterilizing, and cooling medium materials, spawning the medium materials with mycelia to produce a culture medium, and packing the culture medium.
2. Description of the Relevant Art
Some mushrooms have traditionally been cultivated on logs. Various improved mushroom cultivation processes have been proposed. According to one process, for example, mushrooms are cultivated by producing a culture medium by adding nutritional elements such as rice bran to sawdust, filling the medium materials in a small container, heating the medium materials to sterilize the same, cooling the medium materials, and spawning the medium materials with mycelia of the mushroom. This cultivation method is however tedious and time-consuming in that the culture medium has to be manually filled in containers. Since the culture medium is prepared in the atmosphere, it is difficult to prevent various bacteria from entering the culture medium. Inasmuch as the culture medium filled in the container is heated, it takes a considerable time to heat the central area of the culture medium. In addition, the surface area of the culture medium tends to be overheated, whereas the central area thereof tends to be insufficiently heated. If the culture medium is excessively heated, hemicellulose in the sawdust is thermally decomposed into formic acid, which adversely affects the growing of mushrooms. If the heating of the culture medium is insufficient, various germs are developed in the culture medium and contaminate the same.
Japanese Laid-Open Patent Publication No. 55-2243 discloses an apparatus for manufacturing a culture medium for cultivating mushrooms. The disclosed apparatus includes a closed container housing an agitator. The container is supplied with sawdust and rice bran, for example, from a plurality of medium material tanks via feed pipes, and also with water from a water tank. The medium materials and water thus supplied to the container are then agitated and mixed. The container is associated with a jacket which is supplied with steam under a certain pressure from a boiler for sterilizing the medium materials in the container with heat. Since the medium materials are agitated at this time, they are uniformly heated in the surface and central areas. Thereafter, the jacket is supplied with cooling water for cooling the medium materials down to a suitable temperature. Then, the medium materials are fed to another closed container which is of substantially the same structure as that of the aforesaid closed container. The other closed container is heated and cooled before it is supplied with the medium materials. After the other closed container has been cooled to 15.degree. C or below, the medium materials supplied to the other closed container are spawned with mycelia of the mushroom, and the agitator is operated to mix the mycelia in the medium materials thereby to form a culture medium. The produced culture medium is divided into suitable quantities that are then filled in containers. In the disclosed medium manufacturing apparatus, since all of the manufacturing steps are carried out in the closed containers, no various germs can find their way into the medium materials as they are processed into the culture medium. After water has been added to the medium materials, the medium materials are sterilized with the heat of supplied steam. Since the thermal capacity of the culture medium is increased, an increased amount of thermal energy has to be applied during an increased period of time in sterilizing the medium materials. More importantly, only one of the processing steps is performed at a time in the apparatus. Stated otherwise, while a certain step is being carried out, the other steps are not. Such a batch process is of low efficiency.